Permeability μ of a magnetic substance can be obtained by obtaining a magnetic field H and a magnetic flux density B of the magnetic substance and by using a known relational equation B=μH in the electromagnetic theory. As a measurement method in principle, for example, a material to be measured is formed into a toroidal core, and the magnetic field H is obtained from a current flowing in a coil wound on the core, and the magnetic flux density B is obtained from a voltage which is detected as a result of the variation of the magnetic flux. Thus, it is possible to obtain the permeability μ of the material to be measured.
For example, in Patent document 1 shown below, there is disclosed a configuration in a permeability measurement method using the above-mentioned principle, to measure the permeability simply without forming the material to be measured into a toroidal shape. Specifically, as disclosed in FIG. 5, the permeability of the material to be measured is measured by: forming a magnetic path to form a magnetic potential at a gap portion of a reference coil; generating magnetic flux on the magnetic path; detecting the magnetic flux in the magnetic path by a pickup coil; mounting the material to be measured on the gap portion of the magnetic path formed with magnetic flux generated by the reference coil; and detecting a variation of the magnetic flux of the pickup coil depending on the presence or absence of the material to be measured at the gap portion.
Also, in Patent document 2 shown below, there is disclosed a method for obtaining the permeability of a material to be measured by disposing the material to be measured in the vicinity of a coil of an LC resonant circuit in a non-contact manner, and extracting a variation of a resonant frequency as a phase difference, by using that the inductance of a coil is varied depending on the permeability of the material to be measured, so as to obtain the permeability of the material to be measured.
Further, in Patent document 3 shown below, there is disclosed an invention, which was devised by the inventors of the present invention, in regard to an apparatus for measuring a nonlinear dielectric constant in a microscopic area of a dielectric, a material to be measured, through the variation of the capacity of a capacitor in a resonator. However, the above apparatus is not aimed to measure the permeability of a magnetic substance.
Patent document 1: The official gazette of the Japanese Unexamined Patent Publication No. 2003-121419.
Patent document 2: The official gazette of the Japanese Unexamined Patent Publication No. 2002-296240.
Patent document 3: The official gazette of the Japanese Unexamined Patent Publication No. Hei-8-75806.